Fitzpatrick, who has been plagued with injury this season and had just returned following concussion protocols, had come on for the injured Ricky Lutton after 38 minutes.
But the 30-year-old had to come off on the hour after suffering palpitations. Ulster Rugby said a procedure to correct the irregular rhythm had been successful, but he will undergo further tests in Belfast as standard procedure.
The loss of Fitzpatrick until further notice is a blow to Ulster who are suffering an injury crisis, particularly in the front row. Callum Black and John Afoa could be out for the rest of the season, while Lutton has a toe injury that makes him a doubt for the clash with Leinster on Friday week. Loosehead Tom Court (thumb) is expected to return to training some time this week.
Meanwhile, Joe Schmidt has ruled out the possibility of forcing Connacht’s Robbie Henshaw into moving provinces mid-contract for the benefit of the Irish national team.
Henshaw signed a three-year deal with Connacht earlier this season, but recent comments from IRFU president Pat Fitzgerald suggested Henshaw could be forced to move if Schmidt insisted on it.
However, after Connacht Rugby and the new IRFU performance director David Nucifora last week moved to deny Henshaw was going anywhere, Schmidt has also distanced himself from the claims.
“You know, Robbie makes his own decisions and if his playing services are contracted somewhere, that’s where they’re contracted,” said Schmidt.
“I think there can never be a totally linear progression because there’s going to be the odd dip and there’s going to be the odd time where he runs into a bit of a wall and he has to work his way through it.
“But he’s worked his way through a heck of a lot of things really positively so far,” said the Ireland coach.
Schmidt was in Galway on Saturday to run his eye over Henshaw and the rest of his Irish qualified players in action for the home team and Munster and he admitted he continues to be impressed with the 20-year-old.
“I thought he played really well. He did some great defensive work. He was unlucky when Gerhard van den Heever pilfered that offload but he ripped a great ball to save a try so he kind of got that one back.
“He was very strong in the air. His passing game was very good and he was always a threat carrying the ball and he’s also a great young kid.”